A tire of a vehicle may be punctured by a hard object on the road, and the punctured tire may roll unsteadily. This situation may cause a traffic accident and do physical harm to the driver of the vehicle. In order to avoid this situation, a kind of liquid sealant is developed. As a temporary emergent method, the liquid sealant can be used for repairing the punctured tire, so that the vehicle can continue to travel until reaching a repairing station.
At present, the liquid sealant on the market can be made according to various formulations. Most current formulations of the liquid sealant contain natural latex. For example, the invention patent U.S. Pat. No. 6,344,499 B1 discloses a kind of sealant comprising 55-60 wt % deproteinized natural latex. Another invention patent U.S. Pat. No. 6,992,119 B2 discloses a kind of sealant comprising 30-60 wt % natural latex. For the sealing purpose, various kinds of tackifier such as aromatic terpene resin or phenol resin can be added to the sealant, as pointed out by the invention patent U.S. Pat. No. 6,864,305 B2. Additionally, the invention patent U.S. Pat. No. 8,148,448 B2 discloses that 20-40 wt % VEVA copolymer resin can be used as the tackifier. The invention patent US 20120277364 A1 discloses that other materials, such as synthetic latex, can also be used as the tackifier.
As the liquid sealant may be applied at a wide temperature range, most kinds of the liquid sealant comprises anti-freezing agent. The choice of the anti-freezing agent is critical for determining whether the liquid sealant has a lower viscosity or not. In the invention patent U.S. Pat. No. 6,344,499 B1 and the invention patent U.S. Pat. No. 6,864,305 B2, ethylene glycol or propylene glycol can be used as the anti-freezing agent. However, since ethylene glycol is toxic to the environment, ethylene glycol is not preferable. The patent U.S. Pat. No. 7,388,041 B2 and the patent U.S. Pat. No. 8,183,309 B2 disclose glycerin, 1,3-propanediol, and other anti-freezing agents respectively. To further reducing the viscosity, the patent U.S. Pat. No. 7,388,041 B2 discloses that potassium acetate can be added into glycerin so that using less quantity of glycerin can achieve the same anti-freezing effect as using a large quantity of pure glycerin.
Furthermore, to improve the sealing performance, solid components can also be added into the liquid sealant. For example, in the sealant formulation disclosed by the patent U.S. Pat. No. 7,868,061 B2, 2.5-10 wt % fiber material is added into the sealant, and the latex component is reduced to 1-10 wt %. In another invention patent U.S. Pat. No. 7,589,135 B2, a kind of sealant comprising synthetic short fibers and rubber latex is disclosed.
Except the sealing performance, the stability of the liquid sealant is also important, particularly in the liquid sealant comprising natural latex. Surfactant can be added into the liquid sealant to improve the stability of the liquid sealant. In general, anionic surfactant added into the liquid sealant can achieve a superior stabilizing effect, but it would result in a high viscosity of the liquid sealant, especially at a low temperature. Thus, the patent U.S. Pat. No. 8,242,196 B2 mentions that it is preferred to use nonionic surfactant. The invention patent U.S. Pat. No. 8,470,909 B2 discloses a combination comprising both anionic surfactant and nonionic surfactant, which is configured for improving the stabilization of the liquid sealant.
Although a number of sealant products have been developed, most of them contain solid contents with large mass percentages (above 15 wt %). When these sealant products are used, they may cause environmental pollution problems or cleanliness problems. However, other sealant products may be unstable or have not a good tire sealing effect at a wide temperature range. Furthermore, the use of sealant comprising toxic components such as ethylene glycol is undesirable, and solid particles and fibers used in sealant may cause sedimentation problems.